It is important to degas the cooling liquid in the cooling circuit of an internal combustion engine, eg. as is used in a motor vehicle. This is to prevent bubbles of gas or air collecting in the cylinder head which leads to "hot spots" that cause premature wear of the engine. The cooling liquid is usually degassed in the heat exchanger which constitutes the radiator of the cooling circuit. When the radiator is of the type comprising a bundle of parallel tubes running between water boxes fitted at each of their ends, the bubbles of air or gas present in the cooling liquid collect in the top of one of the water boxes, and in general in the water box which does not include the liquid inlet tube to the heat exchanger. Degassing is performed bymeans of a degassing conduit or passage having one end opening out into said top part of said water box where the bubbles of air or gas collect, and having its other end connected to an expansion chamber which is associated with the heat exchanger. The reduced pressure in the expansion chamber sucks the collected bubbles of air or gas from the top of the water box into the expansion chamber.
A first way of forming degassing passages or conduits is simply by providing a hole through a partition wall which separates the water box from the expansion chamber, provided they are side by side in the same housing. A second, and preferred way, is by providing a short length of tube which is fixed in the water box by any suitable means and which has its top end opening out into the space where bubbles of gas or air collect while its bottom end opens out into the expansion chamber below the level of the cooling liquid under normal operating conditions. The second way avoids air or gas being returned to the cooling circuit when the engine is stopped.
However, placing and fixing a degassing tube in a heat exchanger complicates assembly thereof and increases its cost.
Preferred embodiments of the present invention avoid this drawback in a simple and cheap manner.